Motor controller

Abstract

Provided is a technology capable of ensuring drivability of an electric vehicle while preventing thermal destruction of its parts and deterioration of a battery, caused by an LC resonance. The present specification discloses a motor controller for an electric vehicle having a battery, a converter circuit, an inverter circuit, a smoothing capacitor, and a motor, the motor controller configured to control a drive of the motor by controlling an operation of the inverter circuit. In this motor controller, an operating region of the motor that causes a resonance of an LC circuit configured by a reactor of the converter circuit and the smoothing capacitor is set as a resonance region. In this motor controller, execution of square-wave control on the motor is permitted only over a predetermined time period, when the converter circuit is not boosting the DC power and an operating point of the motor is included in the resonance region.

Description

[0001]This is a 371 national phase application of PCT / JP2011 / 074731 filed 26 Oct. 2011, the contents of which are incorporated herein by reference.TECHNICAL FIELD[0002]The present specification relates to a motor controller.BACKGROUND ART[0003]Electric vehicles in which power of batteries thereof is boosted by converter circuits and supplied to motors have been known. These types of electric vehicles each have an LC circuit configured by a smoothing capacitor that smoothens a voltage increased by the converter circuit and a reactor of the converter circuit. A resonance of the LC circuit (LC resonance) causes a current flowing therethrough to oscillate with a large amplitude and at a high frequency, overheating parts of the electric vehicle and deteriorating the battery. For this reason, the occurrence of an LC resonance needs to be prevented as much as possible in order for the electric vehicle to operate.[0004]In many electric vehicles, sine-wave PWM control system and square-wave ...

AI Technical Summary

Benefits of technology

[0007]An electric vehicle sometimes must operate in some circumstances where its inverter circuit needs to be thermally protected or where its converter circuit breaks down and thus cannot boost a voltage. In such a circumstance where voltage boosting is not possible, the region to which the sine-wave PWM control system can be applied becomes narrow, and the resonance region falls outside the region to which the sine-wave PWM control system can be applied. In this case, completely prohibiting the execution of the square-wave control system in the resonance region disables the output of a desired torque to the motor, degrading the drivability of the electric vehicle. Expected is a technology that is capable of ensuring drivability of an electric vehicle while preventing overheating of its parts and deterioration of its battery caused by the LC resonance.

[0009]According to the motor controller described above, the square-wave control of the motor is permitted in the resonance region over the predetermined time period, so that a torque output by the motor is prevented from dropping and that drivability of the electric vehicle is ensured. In this case, although an LC resonance occurs as a result of the execution of the square-wave control on the motor, the execution of the square-wave control is prohibited after a lapse of the predetermined time period. Therefore, the LC resonance can be terminated before parts of the electric vehicle overheat or the battery deteriorates. This motor controller is capable of ensuring drivability of the electric vehicle while preventing overheating of the parts and deterioration of the battery caused by the LC resonance.

[0011]When the LC resonance occurs, the battery repeatedly outputs a large current, which gradually lowers the voltage of the battery. The motor controller described above, however, permits the execution of the square-wave control of the motor while the voltage of the battery is higher than the lower limit value, and prohibits the execution of the square-wave control of the motor when the voltage of the battery lowers and falls below the lower limit value as a result of the continuous LC resonance. The motor controller described above is capable of ensuring the drivability of the electric vehicle while preventing the thermal destruction of the parts and the deterioration of the battery caused by the LC resonance.

[0013]The motor controller described above is capable of ensuring the drivability of the electric vehicle while preventing the thermal destruction of its parts and the deterioration of the battery caused by the LC resonance.

Problems solved by technology

An electric vehicle sometimes must operate in some circumstances where its inverter circuit needs to be thermally protected or where its converter circuit breaks down and thus cannot boost a voltage.

In this case, completely prohibiting the execution of the square-wave control system in the resonance region disables the output of a desired torque to the motor, degrading the drivability of the electric vehicle.

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